Recent rapid development of the biotechnology expands a demand of a flow cytometer and a cell sorter which are more commonly used in the various fields of medicine and biology for automatic analysis and fractionation of multiple cells. In general, the flow cytometer forms a stream of a sheath flow containing various cell particles in line, which are collected from a living body (blood, etc.) and dyed with a fluorescent labeling reagent, and emits laser beam onto the stream of the cell particles to detect light excited by and/or scattered at the cell particles (i.e., forward-scattered light, and side-scattered light, and multicolor fluorescence varying based on the fluorescent labeling reagent used) so that each of the cell particles in the stream is analyzed based upon the detected light In general, the flow cytometer converts the detected light having identification information of the cell particles into electrical signals, so as to statistically evaluate electrical signals for a mass of the cells collected from the sample, thereby allowing diagnosis of a health condition such as a disease of the living body. Further, the cell sorter also uses the electrical signals having identification information to selectively charge droplets containing a particular group of the cells to be sorted, and applying a DC electric field across a dropping path of the droplets, thereby selectively retrieving or sorting the desired cells.
Typical flow cytometers have been suggested, for example by Patent Documents 1 and 2 commonly assigned to the present applicant, all of which disclosure are incorporated herein by reference.
Such conventional flow cytometers or cell sorters have a main or principal purpose in identifying or sorting relatively bulky cell particles collected from the blood. Meantime, as gene analysis research such as human genome decoding research has been more intensively progressed, more demand has been grown for a new technique to identify and sort not only the bulky cell particles but also fine protein complexes precisely by the fluorescent labeling approach.